The present invention relates to pumps in general, and particularly to a pump which is especially suited for pumping fuel from a storage tank to an internal combustion engine.
There are already known fuel pumps which include an impeller wheel including an annulus of impeller vanes or blades, and an end wall which is provided with a lateral pumping channel which is associated with the impeller vane annulus, the end wall being arranged in juxtaposition with an axial end face of the impeller wheel which extends parallel to the plane of rotation of the impeller wheel.
In the conventional pump constructions of this type, a tilting moment about a tilting axis normal to the axis of rotation of the impeller wheel acts on the impeller wheel, owing to the exposure of the latter to the pressure of the fluid being pumped, this pressure increasing in the downstream direction of the pumping channel as a result of the action of the impeller vanes on the fluid being pumped. This tilting moment results in a unilateral loading of the impeller wheel, so that the latter is tilted (immediately within the bearing play) about the tilting axis out of the intended plane of rotation. As a result of this tilting, the impeller wheel comes into contact with and drags along the end wall. In this manner, the mechanical losses attributable to friction increase. Moreover, the size of the axial gap or interface between the impeller wheel and the end wall, which is important for the pumping capacity of the pump of this type, is unilaterally increased. This, of course, is very disadvantageous since it results in a lower throughput and efficiency of the pump and an increased wear of the components which, in turn, results in an even larger increase in the size of the gap and, consequently, a further loss in the pumping capacity.